text: Emil Witzenmann was considered the inventor of expansion joints. 
  In 1920, he applied for a patent for the first so-called flexible metal tube expansion joint, German Reichspatent No. 367 185, from 29 July 1920. From a technical point of view, this precursor of today's expansion joints is a large, pressure-tight flexible metal hose with a defined, restricted freedom of movement. 
  In the 1930s, the metal hose or flexible metal tube principle was replaced by the metal bellows as the central functional element. This design principle – metal bellows with connection pieces – is still the structural basis of modern metal expansion joints today.
  However, records now show that a factory was Founding of Henri Ehrmann & Co. a factory for metal cartridges in Karlsruhe / Germany in 1872.
  In 1898 A patent was applied for "flexible metal tubes with beading folds" (convolutions), Production of bellows and metal hoses of seamless corrugated tubes for industrial applications, was therefore first ever manufacturer by, the company now known as, The BOA Group.